The present invention relates generally to the construction and configuration of electrical machines including motors and generators. More specifically, the invention relates to an AC electrical machine featuring high output power, increased efficiency, and reduce size as a result of incorporating a diamagnetic rotor assembly having a trapped magnetic field.
Traditionally, AC machines have used either permanent magnet rotors or DC excited wound rotors to produce a rotating magnetic field linking stator windings mounted about the rotor. With the introduction of high magnetic strength permanent magnets, it became possible to build higher power density permanent magnet electrical machines as for example J. Denk, U.S. Pat. No. 4,709,180 herein incorporated by reference. These types of permanent magnet machines make efficient use of permanent magnets having a magnetic energy product up to 45 mega-gauss orsted, which are the strongest magnets presently available. There appears to be an upper limit on the magnetic product available from these new magnetic materials. Thus, the maximum power density for permanent magnet machines making use of the new magnets will also be limited.
It is therefore apparent that in order to significantly improve the power density of electrical machines of this type, the magnetic energy product of the rotor must be significantly increased.